Expanding projectiles or bullets as known in the art have several advantages over bullets which are not designed to promote expansion, such as “full metal jacket” or “round nose” bullets. For example, when an expanding bullet travels through a target, it can expand, transferring its kinetic energy to the target. Since an expanding bullet can transfer more of its kinetic energy to the target than can a round-nose bullet, for example, an expanding bullet is less likely to exit the target and cause undesired damage. Accordingly, expanding bullets are useful in military, law enforcement, and sporting applications.
Hollow-point bullets are expanding bullets that contain a cavity or “hollow-point” at the front of the bullet. Upon striking a target, the hollow point fills with material from the target, in effect creating a “wedge” or “penetrater” out of the target material. As the hollow-point bullet travels through the target, the target material is forcefully driven into the hollow point, expanding the front of the bullet. In this manner, a hollow-point bullet with sufficient kinetic energy can expand well beyond its original diameter. Further, the loss of kinetic energy due to expansion slows the velocity of the hollow-point bullet, making it less likely that it will exit the target and cause unintentional damage. At a sufficiently high velocity a hollow-point bullet may break into two or more pieces, or fragment, while it is traveling through the target, transferring a large portion of its kinetic energy to the target while further reducing the likelihood of unintentional harm.
Hollow-point bullets have several drawbacks. If bullet velocity is not optimal, then the front of the bullet may only slightly expand, or not expand at all. Hollow-point bullets often fail to expand when the hollow point becomes clogged with certain types of target material, such as heavy clothing or drywall. Often, the forward part of a hollow point may expand slightly and then be sheared off, leaving a cylindrical projectile to travel through and exit the target, transferring less kinetic energy to the target and increasing the likelihood of unintentional harm.
To promote bullet expansion, some projectiles utilize a wedge-like solid “ballistic tip” or “penetrater” at the front end of the bullet. Upon striking a target, the penetrater is driven into the bullet, causing the front of the bullet to expand. At sufficiently high velocities the penetrater of a ballistic-tip bullet may be driven far enough within the bullet to cause fragmentation, reducing the chance for unintentional harm. However, if bullet velocity is not optimal, then the front of the bullet may only slightly expand, or not expand at all. Often, the forward part of a ballistic-tip bullet may expand slightly and then be sheared off, leaving a cylindrical projectile to travel through and exit the target, transferring less kinetic energy to the target and increasing the probability of unintentional harm.
Some projectiles in the art use a cylindrical fluid-filled cavity to exert a radial expanding force. Fluid-filled bullets can offer advantages over hollow-point and ballistic-tip bullets. First, there is no hollow point to clog or malfunction as in a hollow-point bullet. Second, fluid-filled bullets can expand more rapidly than either hollow-point or ballistic-tip bullets. Fluid-filled bullets can offer greater expansion at a given velocity than either a hollow-point or a ballistic-tip bullet.
U.S. Pat. No. 5,349,907 to Petrovich discloses a projectile having a cylindrical cavity containing a fluid and a shaft at the front of the cavity. Upon impact, the shaft is driven into the fluid, exerting a radial force on the projectile. U.S. Pat. No. 3,429,263 to Snyder discloses a plastic bullet for dispensing paint onto the surface of a target, with the bullet carrying the paint in a tubular cavity. U.S. Pat. No. 6,675,718 to Parker teaches a method for making a fluid-filled projectile by first assembling a fluid-filled cylinder or capsule, and then inserting the cylinder into a hollow cavity of a bullet.
Despite the potential advantages of fluid-filled bullets as conventionally taught, they have had extremely limited commercial success. One reason for the lack of success is the fact that conventional fluid-filled bullets exhibit unpredictable expansion and minimal penetration. Penetration and expansion are important factors when the military, law enforcement agencies, or hunters choose which bullet they are going to use. Unfortunately, bullets that penetrate often exhibit poor expansion and vice-versa. For example, conventional hollow-point bullets may rapidly expand but exhibit poor penetration through car doors, armor, or similar targets. On the other hand, armor-piercing or fully-jacketed rounds may show good penetration through body armor or bone, for example, but generally do not expand reliably and therefore do not transfer maximum kinetic energy to the target.
Accordingly, there is a need in the art for projectiles that can offer enhanced expansion, penetration, or a combination of both penetration and expansion. Such a projectile would be useful in numerous military, law enforcement, and sporting applications.
All the references described above and below are incorporated by reference in their entirety for all useful purposes.